This invention relates to electroconductive polymers, electroconductive materials and processes for preparing electroconductive paper.
Electroconductive paper may be used for a variety of purposes. Nonimpact printing processes such as electrostatographic, electrophotographic, electrographic, "Electrofax" and other processes call for the placement of an electric charge on the paper. In electrophotography, the paper contains a photo-responsive or photoconductive layer of material, such as a specially treated zinc oxide which causes the charge to be dissipated in an area where light strikes it, thus leaving a pattern of the charged areas which is a reproduction of the image desired. The charged area attracts a powdered or other usually particulated image-forming material which may be fused or otherwise treated to make the image permanent. In electrography, electrostatics are used without radiation. The electrical charge is deposited only in the imaged areas. The common characteristic of all of these processes is the use of an electrically conductive base paper.
Similarly, dielectric paper has a substrate which may be paper or plastic, an electroconductive coating and a top dielectric coating which will accept and hold an electrical charge until the paper is contacted with toner.
In the present methods of preparing dielectric and other forms of electroconductive paper, the substrates are coated with an aqueous conductive coating formulation and topcoated with solvent based dielectric or photoconductive, i.e. zinc oxide formulations. This method has many disadvantages, such as the high cost of energy related materials associated with solvent coatings, the increased fire hazards of organic solvents, the high cost of solvent recovery systems and slower coating speeds which are characteristic of solvent based coating systems.
The use of an aqueous topcoat in conjunction with an aqueous conductive coating is impractical when the topcoat is applied directly on the conductive layer. Migration of the conductive species occurs during the topcoating causing a breakdown of the aqueous dielectric emulsion and/or poisoning of the dielectric topcoat.